Posture-Dependent 24-Hour Intraocular Pressure Fluctuation Patterns in an Intraocular Hypertension Monkey Model

Abstract

Purpose We investigate 24-hour intraocular pressure (IOP) fluctuation patterns and the influence of body position on IOP in a chronic ocular hypertension (COHT) monkey model. Methods We recorded 24-hour IOPs (nine time points) in the different body positions in 10 eyes with normal and eight with high IOP (with random selection of one eye of each monkey) using a Tonopen. The IOPs at various time points and in different body positions were compared. Results The average 24-hour IOPs in the immediate-supine, 10-minute supine, 10-minute seated, and immediate-seated positions in the COHT models were 28.64 ± 9.82, 25.42 ± 7.62, 23.49 ± 7.67, and 20.53 ± 7.80 mmHg, respectively. The diurnal-to-nocturnal IOP changes were 8.51 ± 2.93, 5.81 ± 3.67, 5.48 ± 2.97, and 3.59 ± 2.74 mmHg, respectively. The sudden shift between the supine and seated positions bring greater IOP variations (8.11 ± 2.85 mmHg) in the COHT monkeys, and the IOP fluctuations reached 14 to 38 mmHg when considering body position and the measurement time points. Conclusions The measurement time and body position influenced IOP. More elevated IOP occurred in the immediate-supine position and during the transient shift between the seated and supine positions. Maintaining a fixed position for sufficient time before measurement is important. Translational Relevance Glaucoma patients should focus on the importance of IOP measurements in the clinic occurring after an adequate amount of time in a fixed body position.